The present invention relates generally to suspension systems and, more particularly, to jounce bumper plates for use with hydraulic dampers in vehicular suspension systems.
In automotive applications, hydraulic dampers are used in combination with coil springs to absorb relative displacements between a sprung component, such as an automotive vehicle body, and an unsprung component, such as a wheel assembly or vehicle chassis, to absorb the shock of impact sustained by the unsprung component. Vehicular suspension systems utilize various types of well-known hydraulic dampers including shock absorbers and struts.
In a typical strut suspension system, the strut is mounted between the vehicle chassis and the vehicle body. The strut typically includes a hydraulic cylinder with an attached piston and piston rod. The piston rod slidably extends from the upper end of the hydraulic cylinder and is connected to the vehicle body through a flexible connection. The hydraulic cylinder is attached to the vehicle chassis at the lower end of the cylinder. The impact of shocks from the road surface causes movement of the piston through fluid contained in the hydraulic cylinder. The resistance of movement of the piston through the cylinder is proportional to the rate of displacement, thereby damping the movement of the associated spring and preventing excessive bouncing of the vehicle body.
Since displacement of the vehicle chassis causes displacements of the strut, the strut undergoes cycles of compression and extension in response to the displacement of the vehicle chassis. Provision must be made for protecting the strut assembly and the vehicle body from the extreme jounce forces associated with severe irregularities in the road surface. A strut is typically provided with a jounce bumper mounted axially on the piston rod and ajounce bumper plate mounted on the upper end of the hydraulic cylinder. The jounce bumper is an elongated, generally cylindrical member of a compressible, elastomeric material that extends around the piston rod. During jounce motions of the strut, the damper bottoms out and the jounce bumper moves into contact with the jounce bumper plate and compresses to dissipate energy.
The jounce bumper and jounce bumper plate assembly are configured to protect the upper end of the hydraulic cylinder and the rod seal assembly. Jounce bumper plates are typically made of steel and are welded to the seal cover on the upper end of the hydraulic cylinder. An annular piston rod seal provides a fluid-tight seal between the seal cover and the piston rod to maintain the working fluid within the hydraulic cylinder. Jounce bumper plates typically have a central bore for receiving the piston rod and are configured to prevent damage to the rod seal from water and other contaminants. Dirt or moisture accumulating on the piston rod can be forced through the rod seal when the jounce bumper moves into contact with the jounce bumper plate and compresses the air between the jounce bumper plate and the seal cover. Therefore, jounce bumper plates typically provide a gap or channel between the jounce bumper plate and the seal cover that facilitates expulsion of contaminants and water that become trapped within the central bore of the jounce bumper plate.
Conventional jounce bumper plates are prone to deformation under the greater loads associated with recently developed active suspension systems and larger, heavier vehicles. Deformation of the jounce bumper plate around the seal cover inhibits the expulsion of water and other contaminants from the seal area and also results in a rough contact surface during the initial deflection of the jounce bumper. Therefore, there is a need for a jounce bumper plate which provides a smooth structural impact area for the jounce bumper with reduced plate deformation and improved wear characteristics at the jounce bumper/plate interface, allows proper venting to remove debris and other contaminants from the damper seal location, prolongs damper life by protecting the seal area of the damper and improves jounce bumper "entry feel" by providing a smooth interface where the jounce bumper contacts the jounce bumper plate.